Updated 4:13 pm, Monday, September 22, 2014

Just after 11 p.m., 24-year-old Diana Quezada Martinez of Pittsburg had car trouble and stopped on the right shoulder of the Rudgear Road on-ramp onto southbound lanes of the interstate, the CHP said.

Martinez put on her hazard lights and called a co-worker for help before getting out of the car, authorities said. She then stood in a traffic lane of the on-ramp and was struck and killed by a gray Mercedes that, according to the CHP, was unable to stop.

The driver remained at the scene and cooperated with officers. Alcohol was not thought to be a factor in the collision.

Latest news videos

Authorities closed the on-ramp for two hours while investigators processed the scene.

Latest from the SFGATE homepage:

Click below for the top news from around the Bay Area and beyond. Sign up for our newsletters to be the first to learn about breaking news and more. Go to 'Sign In' and 'Manage Profile' at the top of the page.